Q. Recently we were trying to get a corrosion preventive/slushing oil approved
from one of the auto companies. Our product was rejected owing to its failure in the ED compatibility test
due to cratering. It was showing more number of craters compared to that of
the approved oil. Can you kindly let me know which property of the oil needs
to be addressed in order to clear the test requirements. Do you think that reducing
the surface tension of the oil will help?

A. The most probable cause for the paint craters is surface tension; therefore,
in my opinion I would try to change the surface tension of the oil so that it
allows the paint to properly wet the metal surface. I assume that you know how
to measure the surface tension of the approved oil, in which case your goal
should be to match your oil to the approved one.

Do the automotive companies first run the metal through a surface pretreatment
detergent washer before applying the paint? If so, then perhaps your oil is
not as easy to remove from the surface as the approved oil.

Please get back to me with more details if you are not able to solve your problem.